Vapor-cooled lead and stacks thermal performance and design analysis by finite difference techniques

Abstract

Investigation of the combined thermal performance of the stacks and vaporcooled leads for the Mirror Fusion Test Facility-"B" (MFTF-B) (Figure 1) demonstrates considerable interdependency. For instance, the heat transfer to the vapor-cooled lead (VCL) from warm bus heaters, environmental enclo sure, and stack is a significant additional heat load to the joule heating in the leads, proportionately higher for the lower current leads that have fewer current-carrying, counter flow coolant copper tubes. Consequently, the specific coolant flow (G/sec-kA-lead pair) increases as the lead current decreases. The definition of this interdependency and the definition of necessary thermal management has required an integrated thermal model for the entire stack/VCL assemblies.Computer simulations based on finite difference thermal analyses computed all the heat interchanges of the six different stack/VCL configurations. These computer simulations verified that the heat load of the stacks benefically alters the lead temperature profile to provide added stability against' thermal runaway. Significant energy is transferred tdrough low density foam filler in the stack from warm ambient sources to the vapor-cooled leads.Stack-contributed heat transfer has such a significant influence on lead performance that grossly erroneous conclusions may evolve if vapor-cooled leads are analyzed independent of their stack assemblies. • amt<imr*M-PVIM/MUIICM Comm* DtVMion